The modern world-wide economy is strongly dependent upon storage and transportation of large volumes of goods. Generally box-shaped structures make up the bulk of the storage and transportation means in use today. Cargo containers, railcars, and tractor trailers (also known as semi-trailers) are all typically box-shaped structures formed of a floor, a roof, sidewalls, and front and back walls. Such containers are usually rectangular, have one or more doors, and have a defined interior volume for containing cargo.
Such containers are conventionally formed of materials, such as metal and wood. A conventional semi-trailer, for example, is often formed of steel or aluminum frame members, aluminum sidewalls and roof, and a wood floor. Although these materials provide structural strength, they limit the useful lifetime of the trailer since metal components are subject to corrosion, and wood components are subject to rotting. Moreover, these materials also impart great weight to the empty structure. A typical semi-trailer having a standard length of 53 feet has an average overall weight of 15,000 pounds.
Cargo containers are often limited by the amount of cargo that can be stored or transported therein. For example, U.S. highways typically have a federally mandated maximum weight limit of 80,000 pounds. Thus, the total maximum combined weight of a tractor, trailer, and cargo being shipped on a U.S. highway is 80,000 pounds. The average weight of a conventional tractor is 18,000 pounds. The average weight of a conventional trailer is 15,000 pounds. Knowing the average empty weight of a typical trailer, conventional trailers can only haul around 45,000 to 47,000 pounds of cargo. Thus, the weight of conventional trailers can limit the total amount of cargo that can be hauled. In light of the transportation costs associated with hauling cargo, it would be very useful to be able to have a storage and/or transportation structure, such as a trailer, that is of reduced weight and can thus haul a greater overall weight of cargo, all without substantially forfeiting trailer structural strength. The present invention fills this need.